1. Technical Field
The present invention relates to a passive signal path switching device, and more particularly to a signal path switch and a probe card having the signal path switch.
2. Description of Related Art
A Probe cards are widely used in the testing of electrical connections between two electronic elements. In a test task, the probes contact the device under test (DUT) to transmit signals to a tester.
Because of improvements in digital technology, the speed and throughput of electronic devices is increasing day by day. As a result, the conventional tester, which generates the test signals having a frequency lower than the DUT, cannot process such high-frequency signals. To fix this problem, a modern tester makes the DUT generate high-frequency test signals and receives the test signals through the probe card and the DUT.
As shown in FIG. 1, a conventional probe card has a substrate 70, on which a relay 72 is provided. The relay 72 changes the signal path for the DC test signal of the tester 300 and the high-frequency test signal of the DUT 400. It is well known that the inductance in the line, through which the test signals transmit, is increasing while the line is longer. In other words, while the frequency of the test signal is getting higher, and the test signal has to travel from the DUT to the tester for a long path (for example the test signal travels through the probe 80, the substrate 70, another relay 72, the capacitor 74, another relay 72, the substrate 70, and another probe 80) that generates a large inductance while the test signal is travelling through the signal path. It results in a large resistance in the signal path and a large loss of signal when the test signal is travelling through the signal path. Therefore, the tester receives a weak test signal, and, sometime, results in an error test result. In addition, the relay 72 is active which means that the relay 72 has to be switched by user or by other devices that would not make a switch of the signal path in time and needs power to do the switch.